ABAP_to_the_Future

Implementing Mock Objects 3.2
rd_answer = 'Y'.
ENDMETHOD. "mock user interface implementation
METHOD fire_missile. "Mock External Interface Implementation
* Don't do ANYTHING - it's just a test
ENDMETHOD. "Fire Missile - Mock Ext Interface - Implementation
Listing 3.3 Mock Method Redefinitions of Assorted Real Methods
In this example, you create subclasses of your database a ccess class, your user
interface class, and your external system interface class. Then, you redefine the
methods in the subclasses such that they either do nothing at all or return some
hard-coded values.
Object-Oriented Recommendation
In order to follow one of the core OO recommendations—to favor composition over
inheritance—you should have created an interface that is used by your real database
access class and also have the mock class be a subclass that implements that interface.
In the latter case, however, you have to create blank implementations for the methods
you are not going to use, and that could be viewed as extra effort. Nevertheless, interfaces
are a really Good Thing and actually saveyou effort in the long run. Once you read
books like Head First Design Patterns (see the “Recommended Reading” box at the end
of the chapter), you will wonder how you ever lived without them.
3.2.2 Injection
Usually, classes in your program make use of smaller classes that perform specialized
functions. The normal way to set this up is to have those helper classes as private
instance variables of the main class, as shown in Listing 3.4.
CLASS lcl_monster_simulator DEFINITION.
PRIVATE SECTION.
DATA:
"Helper class for database access
mo_pers_layer TYPE REF TO ycl_monster_pers_layer,
"Helper class for logging
mo_logger TYPE REF TO ycl_logger.
ENDCLASS.
Listing 3.4 Helper Classes as Private Instance Variables of the Main Class
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